In an electrophotographic image forming apparatus, a lubricant may be necessary from the viewpoint of the cleaning property of the photoreceptor. Particularly when used in general offices, from the viewpoint of cost, a lubricant is often added to a toner instead of providing a lubricant coating mechanism as a process. At this time, since the lubricant is applied to the photoreceptor via the toner, it is difficult to uniformly apply the lubricant. Specifically, a lubricant such as an aliphatic acid metal salt particle has a larger particle diameter than other external additives, and is easily released from the toner. In addition, since the lubricant tends to have a positive chargeability, it is more likely to be applied to the non-image area for negatively chargeable toner.
Moreover, unless the lubricant is uniformly applied on the surface of the photoreceptor, there is a problem that a difference in image density occurs between the portion having a high concentration of the lubricant and the portion having a low concentration of the lubricant. In particular, in a charging method using a charging roller, since the lubricant on the surface of the photoconductor is generally liable to be decomposed, there is a problem that a difference in image density occurs remarkably.
Therefore, in the conventional toner, attempts have been made to control the application stare of the lubricant on the photoreceptor by combining a lubricant having a large particle size and a lubricant having a small particle size (see, for example, Patent Document 1: JP-A 2014-228763). However, it did not fully satisfy the demand from the market for reducing the image density difference.